1. Field of the Invention
The present invention relates to a gasketed cover which hermetically seals the joint surface between a cover body and a main body in lightweight equipment, for instance, hard disc equipment of a computer; an electronic equipment cover; and processes for the production of said covers. The gasketed cover and an electronic equipment cover according to the present invention are applied to techniques for hermetically sealing the hard disc equipment of a computer installed inside a robot in an automatic manufacturing line or the like so as to completely keep water and air away therefrom.
The gasketed cover according to the present invention can prevent a noise from being generated by the vibration of the cover body at the time of using the gasketed cover. Moreover, the electronic equipment cover according to the present invention can prevent the difference in pressure from occurring between the inside and the outside of the box type main body at the time of using the aforesaid cover.
2. Description of the Related Arts
The development of electronic equipment in recent years really amazes the persons concerned. The above-mentioned equipment, especially integrated circuits which utilizes semiconductors, such as compactified lightweight hard disc equipment are prone to be readily damaged by moisture or dampness in particular.
Accordingly, the hermetically sealing performance of a gasket is a factor of importance for the performance and durability of the electronic equipment, which gasket is used for hermetically sealing the joint surface between a cover body and a box type main body having built-in integrated circuits mentioned above.
It is customary for the purpose of hermetical sealing to integrate a cover body and a box type main body having built-in integrated circuits into equipment by interposing a gasket which hermetically seals the joint surface between said both the bodies and tightening them with fixing bolts. In general, the gasket is adhesively attached to said cover body by means of a double coated tape or the like, which gasket is placed on the joint surface between said cover body and the main body, and interposed therebetween.
The foregoing constitution, however, has often brought about such troubles that long-term usage of the gasket in question lowers the adhesive force of an adhesive coated onto the double coated tape through degeneration, impairs the hermetically sealing function thereof and at the same time, allows dust or moisture to penetrate into the main body, thus unfavorably causing failure of the electronic equipment.
The cover body is usually formed of a metal such as iron, stainless steel and aluminum. The cover body made of a metal is formed by a method in which any of a variety of metallic plates is subjected to punching work or drawing work by the use of a prescribed pressing mold to put the shape thereof in order, and thereafter the worked metal is subjected to an anti-corrosion treatment by non-electrolytic nickel plating, chromium plating, zinc plating or the like.
In the case, however, where the cover body is formed of any of the metals, various molds to be used for punching work or drawing work are needed, and the method of working a metallic plate for the cover body is limited to the above-mentioned working method, whereby the shape of the cover body is restricted to workable shapes. Hence, it is impossible to design the cover body with intricate configuration such as installing a reinforcing rib to enhance the rigidity of the cover body, reinforce only the flange portion thereof and the like. In addition, the problem still remains unsolved in that the heavy metals such as chromium and nickel, which are used for anti-corrosion treatment indispensable for a metal, involve a strong fear of causing environmental destruction.
On the one hand, the gasket has heretofore been produced by punching sheet-like high density polyurethane foam material into a prescribed shape, and the material which is left after the punching is mostly discarded as a waste material. The conventional procedure just mentioned has involved the problems that the yield is worsened thereby, and the gasket formed with said material has a relatively large compression set, thus making it difficult to maintain the hermetically sealing performance for a long period of time and hence deteriorating the durability of the electronic equipment.
The above-mentioned problem relating to the compression set was solved by the adoption of vulcanized rubber such as butyl rubber and EPDM rubber as a material of construction for a gasket, but the problem still remains unsolved in that an unreasonably long time is required by vulcanization.
Accompanying the tendency of compactification and lightweightness of hard disc drives in recent years, the cover body of electronic equipment has been thin-walled. However, the cover body, when formed with a thin-walled metal plate, increases the vibrational frequency of resonance which is generated accompanying the revolution of a spindle motor, thereby bringing about the problem of noisy sound generated at the time of using a hard disc drive. Notwithstanding said problem of noisy sound, no countermeasure thereagainst has been taken in the conventional gasketed cover and cover body.
With regard to the integrated circuits in recent years which make use of semiconductors such as a hard disc apparatus of a compactified lightweight computer, the apparatus is airtightly sealed inside to keep the inside environment constant. For instance, the inside of a hard disc apparatus is airtightly sealed, and thus the environment therein is kept constant by installing a cover body on the main body of the apparatus. However under a complete airtightly sealed condition, a box type main body of the apparatus is often pressurized inside by the rotation of a hard disc driven by a spindle motor, whereby the internal pressure therein is increased. In the case where the apparatus is used under a low temperature environment, the inside thereof is often brought to negative pressure by the shrinkage of the atmosphere therein. In any of the above-mentioned cases, there is caused pressure difference between the inside and outside of the apparatus.
Such being the case, some contrivance has been made so as not to cause the pressure difference therebetween by placing a breathing hole at one portion of the main body of electronic equipment so as to allow outside air to communicate with the space in the main body. Nevertheless, since there is a danger that the breathing hole allows the penetration of a gas and fine foreign matter that are responsible for malfunction of a magnetic disc caused by its accumulation thereon, it is regarded as being necessary to equip the inside of the breathing hole with a dust prevention filter and/or an adsorbent for said gas {refer to Japanese Patent Application Laid-Open No. 36548/1994 (Heisei-6)}. In addition, there is adopted a method in which the breathing hole is slotted so as to prevent sudden change in the pressure inside the main body {refer to Japanese Patent Application Laid-Open No. 297987/1997 (Heisei-9)}. Such breathing mechanism, although effective in preventing the pressure difference from being caused between the inside and outside of the apparatus, complicates the production steps of the apparatus because of the intricate mechanism, thereby unfavorably increasing the production cost.
Under such circumstances, it is a general object of the present invention to provide a first gasketed cover which is lightweight, excellent in sealing properties, and also efficiently producible at a low cost in high precision and accuracy even for intricate shapes without the need for a troublesome production step.
It is another object of the present invention to provide a second gasketed cover which is capable of preventing the generation of noises due to the vibration of a cover body, and excellent in sealing properties.
It is still another object of the present invention to provide an electronic equipment cover which is capable of preventing pressure difference from being caused between the inside and the outside of the main body of the above-mentioned electronic equipment with an inexpensive mechanism without placing a complicated breathing mechanism when pressure variation is caused inside or outside the main body thereof.
Other objects of the present invention will be obvious from the text of the specification hereinafter disclosed.
In view of the above, intensive extensive research and investigation were accumulated by the present inventors in order to achieve the above-mentioned objects. As a result, it has been found that the general object can been achieved by forming a cover body with a thermoplastic resin and at the same time, forming a gasket with a thermoplastic elastomer so as to prepare a gasketed cover in which the cover body is fitted with a gasket.
It has also been found that the object of preventing the generation of noises due to the vibration of the cover body can been achieved by integratedly installing at least one member composed of the elastomer same as that of the gasket on at least part of the plane portion of the cover body excluding the gasket portion so as to prepare a gasketed cover in which the cover body is fitted with a gasket.
It has further been found that the object of eliminating the pressure difference between the inside and the outside of the body of electronic equipment can been achieved by integratedly installing a membrane composed of an elastomer on the plane portion of the cover body so that pressure variation, when being caused inside or outside thereof, can be absorbed by the expansion of said membrane towards inside or outside.
It being so, the present invention has been accomplished by the above-mentioned findings and information.
Specifically, the present invention provides a first gasketed cover comprising a cover body which is composed of a thermoplastic resin and a gasket which is composed of a thermoplastic elastomer, said cover body being fitted with said gasket and integrated therewith.
Further, the present invention provides a second gasketed cover comprising a cover body; a gasket which is composed of an elastic body and integratedly attached to said cover body; and a member which is composed of the elastic body of a type same as or different from that of the gasket and integratedly installed on at least part of the plane portion of the cover body excluding the gasket portion. Further, the present invention provides an electronic equipment cover comprising a cover body and a membrane which is composed of an elastomer and is installed on a hole placed on the plane portion of the cover body, said cover body and said membrane being integrated with each other.